Large area sensing is critical for a variety of military, ecological and commercial interests and has historically been served through the use of centralized long-range sensors. However, rapid improvements in miniaturization of electronic systems have significantly improved the capabilities of small sensor devices. These micro-sensors have the potential to create “large N” distributed networks with advantages in operational adaptability, non-traditional sensing modalities that are only possible with close proximity, increased sensitivity and knowledge extraction through networked intelligence.
While distributed network systems have remarkable promise, their realistic use is limited by risks associated with their accumulation in the environment, detection and defeat, and exploitation due to inability to maintain positive control (unlike centralized long-range sensors).
The phrase “transient electronics” refers to a relatively new family of electronic devices that disappear (disaggregate and disperse) within a set period of time, making them ideally suited for distributed network systems. Conventional transient electronic systems typically rely on the use of soluble substrates and electronic materials (such as silk). When placed into solvent (typically water), these conventional substrates and electronics slowly dissolve into solution. As such, a distributed network system made up of conventional transient electronic devices can be expected to “disappear” over a relatively short amount of time (e.g., after periodic rainfall).
Although the conventional transient electronic approaches achieve the goal of causing the electronics to “disappear” after use, the long dissolution period required to achieve complete disaggregation and dispersal make the conventional approaches unfit for discrete (e.g., military) applications that require rapid and complete disaggregation upon command. Moreover, early conventional approaches utilize materials that were not compatible with existing integrated circuit fabrication and assembly techniques, requiring the development of new IC fabrication processes at significant cost.
More recently, a new type of transient electronic device was introduced in which functional circuitry fabricated using well-known low-cost fabrication techniques (e.g., CMOS or SOI) and disposed on a frangible glass substrate that, when subjected to a small initial fracture force, underwent complete disaggregation (shattering) in a manner that releases sufficient potential energy to also cause disaggregation of the functional circuitry. The transient event (i.e., disaggregation) was controlled by a trigger mechanism configured to generate the required initial fracture force by way of applying resistive heating, a chemical reaction or a localized mechanical pressure to the frangible glass substrate in response to a suitable trigger signal. An issue with some triggering approaches is that they may require a substantial electronic system to provide a particular current or voltage pulse in order to provide the necessary conditions to initiate fragmentation. For example, resistive heating type trigger mechanisms may require a pulse shaping circuit configured to generate and transmit a shaped current pulse from a power source to the resistive heating element in order to generate initial fracture.
What is needed is a simple and reliable trigger mechanism and triggering method for initiating the powderization of a frangible glass substrate in a transient electronic device that reliably achieves complete, on-command disaggregation of the electronic circuitry formed thereon in response to an electronic trigger signal.